1. Field of the Invention
The present invention relates to an image recording material which can be used as a material for a lithographic printing plate, a color proof, a photoresist or a color filter. More specifically, the present invention relates to a negative working image recording material capable of being used for the preparation of a lithographic printing plate by a direct plate making process in which the material is scanned with an infrared laser according to digital signals from a computer or the like.
2. Description of the Related Art
Recently, because of high output power despite their small sizes, a solid laser and a semiconductor laser, which emit infrared rays in the wavelength range of from 760 to 1200 nm, are attracting attention as a recording light source in platemaking directly from digital data of a computer. However, since the sensitive wavelengths of many practical photosensitive recording materials are in a visible light range of 760 nm or less, the above-mentioned infrared laser cannot be used for image recording. Accordingly, there is a demand for an image recording material which can be recorded by means of an infrared laser.
An example of the image recording materials which can be recorded by such an infrared laser is the recording material which is described in U.S. Pat. (hereinafter abbreviated as "US" on occasion) No. 4,708,925 and which comprises an onium salt, a phenolic resin and a spectral sensitizer. This recording material, however, is a positive-working image recording material utilizing an interaction between the onium salt component and the phenolic resin component so that the interaction makes these components insoluble in a developing solution.
On the other hand, an example of a negative working image recording material is described in Japanese Patent Application Laid-open (JP-A) No. 8-276,558. This recording material comprises a substance which absorbs light to generate heat, an alkali-soluble resin and a specific phenol derivative which has 4-8 benzene rings in the molecule. The image recording mechanism is as follows: the substance, which absorbs light to generate heat, converts the light of a laser into a thermal energy and the thus generated thermal energy activates the specific phenol derivative and enables the phenol derivative to act as an initiator of the cross-linking reaction of the alkali-soluble resin so that the alkali-soluble resin is hardened. The drawback of this recording material is that a high-power laser is necessary so as to carry out desired image recording, because the sensitivity of the recording material to a laser is insufficient from the standpoint of energy conversion efficiency.